Humans are the natural reservoirs for Staphylococcus aureus (S. aureus). Healthy individuals can be colonized by S. aureus on the skin, in the nares and the throat either persistently (10-35%), intermittently (20-75%) or be in a non-carriage state (5-70%) with no associated disease. See Vandenbergh et al., J. Clin. Micro. 37:3133-3140 (1999). Disease subsequently occurs when individuals become immunocompromised due to breaches in immune barriers, such as during surgery, placement of indwelling catheters or other devices, trauma, or wounds. The resulting S. aureus infection can cause a wide range of different diseases that range from mild skin infections to endocarditis, osteomyelitis, bacteremia, sepsis, and other forms of disease with accompanying high mortality rates. The large human reservoir enhances opportunity for evolution and spread of adapted pathogenic clonal types.
Invasive staphylococcal infections from the Gram positive cocci S. aureus and S. epidermidis are of particular concern because they are an increasing public health problem worldwide. Specifically, S. aureus is responsible for the majority of hospital-acquired (nosocomial) infections and its prevalence in community-onset infections is increasing. For example, the incidence of invasive methicillin-resistant S. aureus (MRSA) was estimated at 31.8 per 100,000 persons, including 18,650 deaths in the United States in 2005. See Klevens R. M. et al., JAMA, 298:1763-71 (2007).
Staphylococcal diseases have seen a dramatic increase in the last 20 years, this increase parallels the use of intravascular devices and invasive procedures. This rise in disease incidence is made more troubling because of the parallel rise of antibiotic resistance, therefore, there is an urgent need for immunogenic compositions for use in vaccines or to elicit polyclonal or monoclonal antibodies to confer passive immunity as a means to prevent or treat staphylococcal infection and associated diseases.